* c-opts.c (c_common_handle_option): <case OPT_Werror> set
        global_dc->warning_as_error_requested.
        * diagnostic.c (diagnostic_initialize): Tidy.
        * diagnostic.h (diagnostic_context::x_data): Remove
        (diagnostic_context::issue_warnings_are_errors_message): Rename
        from warnings_are_errors_message.
        (diagnostic_context::warning_as_error_requested): New.

From-SVN: r86750